This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Because cadaver organ donor shortage and the inferior results associated with cadaveric transplantation, living donor transplantation is being increasingly emphasized and encouraged. Our goal is to determine the long-term impact of donation of kidney. Living donor kidney transplantation has been done for over 40 years. Short-term studies show no adverse impact on the donor, and long-term studies have suffered from their retrospective design and, therefore, incomplete and possibly biased ascertainment of the outcomes of interest. We would like GCRC assistance in performing iohexol GFR measurements.